One thing my job hunt taught me so far is that React is all over the place (surprise!), except at large companies that have in-house front-end teams working on their own sites. Those companies prefer vanilla JS over frameworks.
Interesting, isn't it?
Recruiters always ask for React, because their clients do. Still, it seems React is mostly added to the skill list by their clients' "full-stack developers" (i.e. Java people), who don't necessarily know a lot about front-end.
We're currently allowing non-front-enders to take crucial front-end decisions, and their silver bullet is React. (Used to be Angular, will become Vue.) The very fact that they're still looking for silver bullets is maybe the most serious problem we have in front-end right now.
Ah, but who tells the business people what kind of business impact specific technical solutions will have? Senior developers, i.e. back-end developers. Business people almost never have the technical skills to decide for themselves.
I have no great faith in the Market as an objective arbitrator, I must admit.
What we'd have to compare is two very similar sites, one created with frameworks and one without, and see which one performs better - also in the sense of page speed, which hugely impacts conversions.
Wouldn't want you to do that, but could you write something with anonymized data?
"E-commerce site X uses React; Y uses vanilla JS; we saw that X's time to first render is 170% of Y's and we estimate this loses them 1,000 transactions per day."
I would like to see solid numbers and figures that support that position, preferably controlled for the experience level of the front-end developers.
I mean, if you're an excellent front-ender you don't necessarily want to work in an environment that doesn't value your knowledge.